I have been reading with interest your ideas for a homegrown pit controller.
So, I have been rooting through the shed and come up with a 12v pid controller, a commercial oven thermistor(rated to 350 degrees C), a somewhat large centrifugal fan, but although it's only 31W, it's 240v. I also have a SSR, which will run the fan.
So I'll run all the 240v stuff off a small invertor, and only have one 12v dc supply. I have some big sealed lead acid batteries, so power is not a problem.
All this will go in a plywood box, which will sit at the side of the drum and connect to the uds with a flexible hose.
If it works it will be great, if not, well it's not been a loss.
I have run it up, connected by all sorts of bodge wiring on the bench, so it works as a going concern, it just needs sticking in a box and making pretty.